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    <title>Document</title>
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    <script>

        // ASCII 字符集


        // charAt(index)   通过下标访问字符串的值
        // charCodeAt(index)  通过下标访问字符串的值的ASCII值


        // String.fromCharCode(n)   把ASCII值转化为对应的字符


        // var str = 'hi';
        // console.log(str.charAt(0));   // str[0]

        // console.log(str.charCodeAt(0));


        // console.log(String.fromCharCode(104));   // 'h'





        var numArr = [];
        for (var i = 0; i <= 9; i++) {
            numArr.push(i + '');
        }


        var smallArr = [];
        for (var i = 97; i <= 122; i++) {
            smallArr.push(String.fromCharCode(i));
        }


        var bigArr = [];
        for (var i = 65; i <= 90; i++) {
            bigArr.push(String.fromCharCode(i));
        }

        var allArr = numArr.concat(smallArr, bigArr);
        console.log(allArr);





    </script>

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